This invention relates generally to transmissions with a hydraulic coupling member and locking clutch, i.e. transmissions of the kind comprising, in parallel between an input element intended to be rotationally integral with a first shaft, (usually the drive shaft) and an output element intended to be rotationally integral with a second shaft, (usually the driven shaft) on the one hand a hydraulic coupling member, such as a torque converter or hydraulic coupler, which comprises an impeller wheel rotationally integral with the input element and a turbine wheel rotationally integral with the output element, and on the other hand a clutch which, on starting up and usually each time the gear ratio is changed, is idle in a first stage and thus first allows the hydraulic coupling member to intervene between the input element and the output element and which, in a second stage, puts this hydraulic coupling member out of action so as to prevent the slipping caused by the latter and thus improve the overall efficiency, by providing a direct mechanical coupling between the input element and the output element.
The invention relates particularly to such transmissions which are intended to be fitted to motor vehicles. These may be either semi-automatic or automatic.
In practice, in the transmissions of the kind in question, the clutch used comprises an axially-movable coupling element which is rotationally integral with the output element and capable of being made rotationally integral, by friction, with the input element. A clutch of this kind may be reduced to this coupling element.
However, more often, although not necessarily, this clutch may also incorporate a torsion damping assembly, for smoothing out the vibrations inherent in the kinematic chain in which it is interposed, this torsion damping assembly comprising two coaxial parts mounted for relative rotation within the limits of a specified angular clearance and against elastic means acting circumferentially between them, one of said parts being rotationally integral with the coupling element whilst the other is rotationally integral with a rigid hub.
For example, one of the rotary parts may comprise an annular flange and the other part may comprise two guide washers provided on both sides of this flange, parallel thereto, and integral with each other, whilst the elastic means provided circumferentially between these parts then consist of springs partly housed in apertures provided in the flange and partly housed in apertures provided in the guide washers.
One of the problems to be solved in producing transmissions of this type stems from the fact that a rotational connection has to be provided between one of the rotary parts forming the torsion damping assembly, on the one hand, and the coupling element, on the other hand, whilst the latter should also be capable of moving axially.
Two solutions are generally adopted to satisfy this requirement.
In one method, a rigid connection is provided between the flange and the hub with which it is associated, and a grooved connection (such as a splined coupling) is provided between the coupling element and this flange.
In a second arrangement, which is more often used in practice, a rigid connection is provided between the coupling element and the flange, and a grooved or splined connection is provided between this flange and the hub which is associated with it. In both cases, a grooved connection is used.
A grooved connection of this kind can give rise to friction and slipping. Moreover, as a result of jamming or blocking, it is liable to operational breakdowns, thus jeopardising the engagement and/or disengagement of the clutch.
It is also known to provide a rotational connection between two elements by means of tabs, this connection comprising a plurality of elastically deformable tabs usually known as tangential tabs, which are each formed by at least one leaf spring and which, being provided substantially tangentially, relative to a circumference of the assembly, in relation to one of the elements which they connect, permit relative axial displacement of these two elements relative to each other, whilst making them rotationally integral with each other.
A tab connection of this kind is usually used, for example, in orthodox dry clutches, between the pressure plate and the cover.
This invention relates generally to the application of a tab connection of this kind to transmissions having a hydraulic coupling and locking clutch of the kind described above, whether or not the clutch incorporates a torsion damping assembly.